METHOD FOR RECLAIMING INSULATED WIRE UTILIZING AGITATION OF A CHLORINATED HYDROCARBON BATH
United States Patent 3877474
Method for reclaiming the metallic inner conductor of insulated wire and cable with substantially no physical damage or oxidation utilizing the combination of a soak in a chlorinated hydrocarbon solution, preferably methylene chloride, wherein a tank containing the solution is agitated to separate the outer organic insulating material from the inner conducting metal, and recycling of the chlorinated hydrocarbon solution by a process of distillation. The recycling after reclaiming the metal, adds substantially to the economy achieved by the method.
US Patent References:
Method of removing plastic coating from a metal article
Canziani et al. - March 1947 - 2417468
Process for removing resin coating from copper wire
Schub - February 1948 - 2435239
Metal stripping process
Crepeau et al. - November 1954 - 2694658
Desealant composition and process
Whittier et al. - September 1958 - 2852471
Reclamation method
Lowry - March 1961 - 2977255
Method of removing plastic coating from a metal article
Canziani et al. - March 1947 - 2417468
Process for removing resin coating from copper wire
Schub - February 1948 - 2435239
Metal stripping process
Crepeau et al. - November 1954 - 2694658
Desealant composition and process
Whittier et al. - September 1958 - 2852471
Reclamation method
Lowry - March 1961 - 2977255
Inventors:
Urssing, Allen H. (Sepulveda, CA)
Despain, William R. (Los Angeles, CA)
Ramos, Henry John (Hollywood, CA)
Despain, William R. (Los Angeles, CA)
Ramos, Henry John (Hollywood, CA)
Application Number:
05/277991
Publication Date:
04/15/1975
Filing Date:
08/04/1972
View Patent Images:
Export Citation:
Assignee:
R&D Metals (Los Angeles, CA)
Primary Class:
Other Classes:
134/29, 134/12, 134/27, 134/38, 134/33, 134/19, 134/14
International Classes:
B08B3/10; C08J11/02; H01B15/00; C08J11/00; B08B3/10
Field of Search:
134/6,10,12,25R,29,38,27,32,33,109,117,2,14,19,118,119,120,121,157,159 15/90,3,1 259/89,90
US Patent References:
| 3067070 | Cleaning method for industrial systems | December 1962 | Loucks | |
| 3455737 | METHOD OF REMOVING A COATING | July 1969 | Seibert | |
| 3610260 | DEGREASING APPARATUS AND METHOD | October 1971 | Kearney | |
| 3624009 | METHOD FOR RECLAIMING COMMERCIALLY USEFUL FIBERS AND RESIN FROM SCRAP MATERIAL | November 1971 | Sussman | |
| 3625763 | CONFORMAL COATING STRIPPING METHOD AND COMPOSITION | December 1971 | Melillo | |
| 3727621 | ROTARY WASHER | April 1973 | Morton |
Primary Examiner:
Bashore, Leon S.
Assistant Examiner:
Alvo, Steven M.
Attorney, Agent or Firm:
Spensley, Horn & Lubitz
Claims:
We claim
1. A method for reclaiming the metallic conducting wire from bales of tangled strands of insulated wire and cable comprising the steps of:
2. The method of claim 1 wherein said chlorinated hydrocarbon is selected from the group consisting of methylene chloride, carbon tetrachloride, ethylene dichloride, monochlorobenzene, ortho-dichlorobenzene, trichlorobenzene, chlorobenzene, propylene dichloride, I,I,I-trichlorethane, perchlorethylene, trichlorethylene and chloroform.
3. The method of claim 1 wherein said tank is agitated by being rotated at a rate in the range from 6 to 72 rpm, whereby said bales therein are subjected to a random cascading motion.
4. The method of claim 3 wherein said tank contains a plurality of internal vanes against which said bales fall during said rotation of said tank, thereby enhancing the separation of said insulating material from said wire.
5. The method of claim 1 including, prior to the step of recovering said chlorinated hydrocarbon, the additional step of adding a neutralizing agent to said bath to neutralize the acidity thereof.
6. The method of claim 1 including the additional steps of (i) adding an acid neutralizing agent to said bath prior to immersing said bales therein, and (ii) adding an acid neutralizing agent to said bath prior to the step of recovering said chlorinated hydrocarbon.
7. The method of claim 6 wherein said neutralizing agent is selected from the group consisting of sodium hydroxide, lithium hydroxide and potassium hydroxide.
8. The method of claim 6 wherein said neutralizing agent is sodium hydroxide, said chlorinated hydrocarbon is methylene chloride, said sodium hydroxide being added to said bath at the rate of 0.4 to 3.0 percent by weight of said methylene chloride.
9. A method for reclaiming the metallic conducting wire from bales of tangled strands of insulated wire and cable comprising the steps of:
10. A method for reclaiming the metallic conducting wire from bales of tangled strands of insulated wire and cable comprising the steps of:
1. A method for reclaiming the metallic conducting wire from bales of tangled strands of insulated wire and cable comprising the steps of:
2. The method of claim 1 wherein said chlorinated hydrocarbon is selected from the group consisting of methylene chloride, carbon tetrachloride, ethylene dichloride, monochlorobenzene, ortho-dichlorobenzene, trichlorobenzene, chlorobenzene, propylene dichloride, I,I,I-trichlorethane, perchlorethylene, trichlorethylene and chloroform.
3. The method of claim 1 wherein said tank is agitated by being rotated at a rate in the range from 6 to 72 rpm, whereby said bales therein are subjected to a random cascading motion.
4. The method of claim 3 wherein said tank contains a plurality of internal vanes against which said bales fall during said rotation of said tank, thereby enhancing the separation of said insulating material from said wire.
5. The method of claim 1 including, prior to the step of recovering said chlorinated hydrocarbon, the additional step of adding a neutralizing agent to said bath to neutralize the acidity thereof.
6. The method of claim 1 including the additional steps of (i) adding an acid neutralizing agent to said bath prior to immersing said bales therein, and (ii) adding an acid neutralizing agent to said bath prior to the step of recovering said chlorinated hydrocarbon.
7. The method of claim 6 wherein said neutralizing agent is selected from the group consisting of sodium hydroxide, lithium hydroxide and potassium hydroxide.
8. The method of claim 6 wherein said neutralizing agent is sodium hydroxide, said chlorinated hydrocarbon is methylene chloride, said sodium hydroxide being added to said bath at the rate of 0.4 to 3.0 percent by weight of said methylene chloride.
9. A method for reclaiming the metallic conducting wire from bales of tangled strands of insulated wire and cable comprising the steps of:
10. A method for reclaiming the metallic conducting wire from bales of tangled strands of insulated wire and cable comprising the steps of:
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the separation of insulating material and metallic components from compositions wherein the two are physically combined; and, more particularly, to an economical method for separating and reclaiming the metallic and insulating materials from the physical combinations thereof which are found in insulated wire and cable.
2. Prior Art
Insulated electrical wire and cable are utilized in large volumes in the electronics, electrical, communications, aerospace, and building industries, to name only a few. Such wire and cable typically comprise an inner metallic conductor encased within an outer sheath of insulating material. Multi-conductor cable, shielded wire and coaxial cable are commonly used variations which also contain metallic conductors and, in the case of shielded wire, metallic shielding. Copper is most frequently used as the inner conductor of wire and cable because of its excellent electrical conductive properties. However, other metals are also used such as, for example, aluminum. Typical insulating materials include rubber, neoprene, polyvinyl chloride, polyethylene and teflon.
Millions of pounds of scrap wire and cable are produced annually in the United States and in other industrial nations from a number of sources. Firstly, as in most manufacturing processes, the fabrication of insulated wire and cable results in a certain amount of rejected scrap material. In addition, scrap is generated by the users of insulated wire and cable as a result of their fabrication processes, the scrapping of obsolete electrical and electronic equipment, replacement of power and telephone lines, the wrecking of buildings, and the rewiring of electrical and electronic systems and equipment. Generally, scrap insulated wire and cable is found in the form of masses of loose strands of varying lengths tangled into large coils or bales. The existence of tons of metal, such as copper, in this form has stimulated efforts to reclaim it economically.
In the prior art, a number of methods are known for the reclamation of metal from scrap wire and cable. The utility of any method for reclaiming such metal is directly related to its cost. For example, if the sum of (i) the cost of reclaiming one pound of copper and (ii) the cost of the scrap wire necessary to yield one pound of copper is equal to or greater than the market value of the pound of copper reclaimed, the method of reclamation has substantially no practical or commercial value. In order to be of maximum commercial value, a method for reclaiming the metal from scrap wire must be both highly cost-effective and also capable of yielding the highest grade of metal, the latter, of course, obtaining for the reclaimant the best price on the metals' market.
One method of the prior art for reclaiming the metal conductors from scrap wire and cable is to remove the insulation manually by cutting and stripping means. Since this method requires each conductor wire to be treated individually, it is relatively slow and costly even on loose wire or cable. When the wire and cable is in the form of tangled coils or bales, the manual stripping method is prohibitive since the scrap would first have to be separated into individual strands prior to processing. In addition to being laborous and costly, this method is most suitable only with respect to wire and cable having larger diameters, such as AWG or MCM sized greater than 8.
A second and common method of the prior art involves combustion of the insulating material to enable the recovery of the metal conductor within the wire or cable. This method has serious practical limitations. In the first place, the metal recovered is charred, i.e., oxidized due to the high temperature required to burn off the insulating material. In the case of copper conductors, combustion results in the loss of approximately 6 percent by weight of the copper which was potentially recoverable. Secondly, the oxidized metal is of a lower grade than unoxidized metal and therefore yields less on the market. Thirdly, the charred insulation, or ash, must be knocked off the inner conductor before the metal is acceptable for smeltering, i.e., marketable. The additional step of knocking off the ash necessarily increases the cost of the method and thereby decreases its commercial value. An additional and very substantial shortcoming of the combustion method is that, without special purpose air pollution abatement equipment, it results in the emission of air pollutants into the air. Many States and other governmental agencies prohibit such emissions. As a result, the reclaimant is required either (i) to transport the scrap to a place where burning is not prohibited or (ii) to install the necessary abatement equipment. In either case, the cost of practicing the method is increased significantly. Lastly, the burning method destroys the insulation and therefore whatever value the insulating material might have is lost.
Another method known in the prior art is to dissolve chemically the insulating material. This method has proved to be relatively uneconomical due to the typically high solids ratio of insulation to inner conductor by weight. For example, the insulation covering a copper inner conductor is typically 28 - 30 percent by weight of the wire. Because of the relatively high solids ratio, the cost of the chemical composition required to dissolve sufficient insulation to yield a pound of metal is too high with reference to the market value of the pound of metal yielded. An additional shortcoming of this method results from the fact that many different insulating materials are used in wires and cables. This fact requires the reclaimant to have various chemical compositions available, each one particularly suited to dissolving a particular type of insulating material.
Still another method of the prior art for the reclamation of insulated wire and cable is disclosed by Wanzenberg in his U.S. Pat. No. 3,342,638, granted on Sept. 19, 1967, involving a special purpose apparatus for heating a mass of insulated wire without burning the insulation, and extruding the insulation while compressing the metal into a solid compact. This method has the disadvantage of requiring the special purpose and relatively complex apparatus disclosed in the aforesaid patent. In addition, this method requires the strands of wire and cable to be assembled in a feed container in substantially parallel linear alignment, a laborous step when the wire to be processed is in the form of a tangled coil or bale.
The present invention accomplishes the objective of reclaiming the metallic inner conductor and the insulating material of scrap wire and cable without the shortcomings and limitations of the prior art. In addition, the metal reclaimed is in its purest form; i.e., it is not degraded by the process of reclamation taught by this invention. Most importantly, however, the present invention enables the recovery of metal at a cost significantly less than has heretofore been possible by the methods known and practiced in the trade.
BRIEF SUMMARY OF THE INVENTION
The present invention is a method for physically separating and reclaiming conducting and insulating materials from structural combinations of the same, such as are found in insulated wire and cable. The invented method is based upon, and is one means for exploiting, the discovery that certain chloronated hydrocarbon solutions cause most of the insulating materials commonly used in wire and cable manufacture to swell and soften. When in a swollen and softened state (as caused by a chlorinated hydrocarbon solution), the insulating materials typically lose their strength and will readily break away from the inner conductor if subjected to a random and cascading motion. A preferred chlorinated hydrocarbon solution is methylene chloride because during the time typically required to remove insulation, it has substantially no effect chemically on copper, the most commonly used metal for the inner conductor of wire and cable. In addition, methylene chloride has only a relatively slight chemical effect on most of the insulating materials used in wire and cable manufacture. Therefore, the use of methylene chloride as a stripping agent also enables the reclamation of the insulating materials, many of which have commercial value such as neoprene and various rubbers. In addition to its low order of reactivity on insulated wire and cable, methylene chloride is also a preferred stripping agent because (i) it can be recovered and recycled inexpensively, thereby adding substantially to the cost-effectiveness of the invented method; (ii) it is readily available throughout the world at a low price; (iii) it has a relatively low toxicity as compared to other chlorinated hydrocarbons; and (iv) it has no flash or fire points.
The present invention, therefore, comprises the process steps of (i) soaking a mass of wire or cable in a bath of a chlorinated hydrocarbon solution, (ii) subjecting the mass to a random tumbling or cascading motion until the insulating material and conducting metal separate; (iii) reclaiming the metal; (iv) recovering and recycling the chlorinated hydrocarbon solution; and (v) reclaiming the insulating material. The reclaimed conducting metal is typically free of residue or contaminants. After recovery, the chlorinated hydrocarbon quickly evaporates. The metal requires no rinsing or other special handling (such as the removal of ash as required by the prior art method of burning off the insulation). The metal is typically of the highest grade and therefore commands a top price on the metals ' salvage market (prior to smelting).
Thus, it is a principal object of the present invention to enable the economical recovery of valuable metals and insulating materials from scrap wire and cable.
It is another principal object of this invention to provide a method for reclaiming insulated wire and cable which does not degrade the quality or reduce the quantity of materials recovered.
It is another object of this invention to provide a method for reclaiming insulated wire and cable which does not require elaborate and expensive special purpose equipment.
It is still another object of this invention to provide a reclamation method which does not rely upon burning, thereby eliminating air pollution constraints on a reclaimant's operation.
A still further object of the present invention is to enable the processing of scrap wire and cable in the form in which it is typically found, i.e., tangled coils or bales, without laborous untangling or other process steps.
Other objects, novel features and advantages of the present invention will become apparent upon making reference to the following detailed description. The description will also further disclose the characteristics of this invention. Although the invention will be described hereinbelow in terms of a particular example, it should be expressly understood that the description thereof is for the purpose of illustration only and does not limit the scope of this invention.
DETAILED DESCRIPTION OF THE INVENTION
For the purpose of greater clarity and understanding, the detail description of the present invention will be made with reference to a particular example, namely the reclamation of copper from scrap wire and cable utilizing as a stripping agent, a nearly 100 percent solution of methylene chloride, the preferred chlorinated hydrocarbon. The methylene chloride solution is not 100 percent because of the addition of a small amount of neutralizer as described more fully hereinbelow.
A bale of scrap insulated wire and cable is first immersed in a bath of methylene chloride solution. Prior to immersion in the bath, the bale of wire and cable requires no processing. However, in order to ensure the recovery of the highest purity of copper, it is preferable to inspect the bale and to eliminate strands of wire or cable which an inspector can readily determine are types which either (i) contain other metal in addition to or instead of copper and/or (ii) utilize insulating materials on which methylene chloride is not effective as a stripping agent such as, for example, teflon.
The tank in which the bath of methylene chloride is contained should be large enough to accommodate the volume of the typical bales of scrap wire and cable which are to be processed. In addition, the tank must be adapted to being (i) mechanically coupled to a source of power and (ii) set into a particular motion by that source of power. A preferred motion is rotation at a rate in the range from 6 to 72 rpm, because such rotation subjects the bale of wire to a random tumbling or cascading motion which is particularly suited to breaking the insulating material away from the copper conductor after the former has been swollen and softened by the stripping agent. The inclusion of internal vanes within the rotatable tank substantially enhances the process of separation because of the impact of the insulated wire against the vanes during rotation. Of course, the tank containing the bath solution and scrap wire must be capable of being sealed so as to avoid any loss of the solution during the rotation or other motion of the tank.
In the first of two alternative procedures, a bale of scrap wire is immersed in the tank containing the bath of methylene chloride at ambient room temperature. The tank is then sealed, the power source to which the tank is coupled is activated, and the solution heated to a temperature of 104° F, its boiling point, by external conventional heating means. At a temperature of 104° F the solution of methylene chloride causes the insulating material on the strands of wire and cable to become swollen and soft. The motion of the tank, preferably rotation, causes the bale of scrap wire to break apart, thereby facilitating the penetration of the solution into the insulation and speeding up the process of stripping by quickening the heat transfer required. For this reason it is preferred that the rotation of the tank start immediately after the tank is sealed. In addition, as indicated earlier, the motion of the tank contributes to the process of breaking the insulating material away from the copper conductor after the insulation has become swollen and softened. Approximately 65 minutes after the start of the procedure described, the separation of insulating materials from copper is usually complete and the copper may be removed from the tank. No rinsing or other processing is required with respect to the copper recovered. The methylene chloride solution on the metal rapidly evaporates.
In an alternate procedure, a bale of scrap wire is placed in an empty tank. The tank is then sealed and immediately activated, preferably rotated, while methylene chloride, preheated to 104° F, is pumped or otherwise injected into the tank. As in the first procedure, it is preferable to activate the tank immediately after it is sealed, for the same reasons. By this procedure approximately 35 minutes is required to separate the insulating material from the copper conductors. Again no rinsing of the copper is required after its removal from the tank.
At this point in the reclamation process, the tank contains the methylene chloride solution and the residue of swollen insulating material. Recovery of the methylene chloride for reuse is a substantial factor in making the invented method more economical than has heretofore been possible. In addition, as indicated earlier, reclaiming the insulating material for subsequent sale further enhances the commercial value of this method. Recovery of the methylene chloride is by distillation; i.e., evaporation out of the tank and condensation in a separate recovery tank. The techniques and apparatus for distillation are well-known in the trade. Typically, about 95% of the original amount of methylene chloride by volume is recovered by distillation. It is of reusable quality and may be recycled indefinitely. After the recovery of the methylene chloride solution, a mass of insulating material remains in the tank. It can be easily removed for further processing or sale.
It has been observed that the methylene chloride solution recovered by distillation is more acidic than pure methylene chloride solution. This is due to the influence of heat, acidic lubricants and soils typically found on the wire. In addition, certain volatile contaminants, produced during the soaking period, are probably not all separated from the methylene chloride during the distillation step. In order to neutralize the increased acidity of the solution, a suitable neutralizing agent is typically added to the solution prior to distillation and when charging the tank in connection with either of the alternative procedures described hereinabove. Suitable neutralizing agents are sodium hydroxide (caustic soda), lithium hydroxide and potassium hydroxide. Caustic soda is a preferred neutralizer because of its general availability and relatively low price. Caustic soda, each time it is added, is typically added at the rate of 0.4 to 3.0 percent by weight based on the weight of methylene chloride; i.e., 0.4 - 3.0 pounds of caustic soda for each 100 pounds of methylene chloride.
This invention also contemplates the addition of an improved neutralizer or "stabilizer," many of which are known in the industry and generally referred to as "antioxidant inhibitors," "neutral acid acceptors" or "acceptors." Such compounds are typically used to prevent hydrolytic, thermal, oxidative and catalytic degradation.
As indicated earlier methylene chloride is a preferred stripping agent. Other chlorinated hydrocarbons suitable for use as the stripping agent in the invented method include carbon tetrachloride, ethylene dichloride, monochlorobenzene, ortho-dichlorobenzene, trichlorobenzene, chlorobenzene, propylene dichloride, I, I, I-Trichlorethane, perchlorethylene, trichlorethylene, and chloroform.
Although this invention has been disclosed and described with reference to a particular example, the principles involved are susceptible of other applications which will be apparent to persons skilled in the art. It will be understood by those skilled in the art that various changes in detail and application of the invented method may be made therein without departing from the spirit and scope of the invention.
1. Field of the Invention
This invention relates generally to the separation of insulating material and metallic components from compositions wherein the two are physically combined; and, more particularly, to an economical method for separating and reclaiming the metallic and insulating materials from the physical combinations thereof which are found in insulated wire and cable.
2. Prior Art
Insulated electrical wire and cable are utilized in large volumes in the electronics, electrical, communications, aerospace, and building industries, to name only a few. Such wire and cable typically comprise an inner metallic conductor encased within an outer sheath of insulating material. Multi-conductor cable, shielded wire and coaxial cable are commonly used variations which also contain metallic conductors and, in the case of shielded wire, metallic shielding. Copper is most frequently used as the inner conductor of wire and cable because of its excellent electrical conductive properties. However, other metals are also used such as, for example, aluminum. Typical insulating materials include rubber, neoprene, polyvinyl chloride, polyethylene and teflon.
Millions of pounds of scrap wire and cable are produced annually in the United States and in other industrial nations from a number of sources. Firstly, as in most manufacturing processes, the fabrication of insulated wire and cable results in a certain amount of rejected scrap material. In addition, scrap is generated by the users of insulated wire and cable as a result of their fabrication processes, the scrapping of obsolete electrical and electronic equipment, replacement of power and telephone lines, the wrecking of buildings, and the rewiring of electrical and electronic systems and equipment. Generally, scrap insulated wire and cable is found in the form of masses of loose strands of varying lengths tangled into large coils or bales. The existence of tons of metal, such as copper, in this form has stimulated efforts to reclaim it economically.
In the prior art, a number of methods are known for the reclamation of metal from scrap wire and cable. The utility of any method for reclaiming such metal is directly related to its cost. For example, if the sum of (i) the cost of reclaiming one pound of copper and (ii) the cost of the scrap wire necessary to yield one pound of copper is equal to or greater than the market value of the pound of copper reclaimed, the method of reclamation has substantially no practical or commercial value. In order to be of maximum commercial value, a method for reclaiming the metal from scrap wire must be both highly cost-effective and also capable of yielding the highest grade of metal, the latter, of course, obtaining for the reclaimant the best price on the metals' market.
One method of the prior art for reclaiming the metal conductors from scrap wire and cable is to remove the insulation manually by cutting and stripping means. Since this method requires each conductor wire to be treated individually, it is relatively slow and costly even on loose wire or cable. When the wire and cable is in the form of tangled coils or bales, the manual stripping method is prohibitive since the scrap would first have to be separated into individual strands prior to processing. In addition to being laborous and costly, this method is most suitable only with respect to wire and cable having larger diameters, such as AWG or MCM sized greater than 8.
A second and common method of the prior art involves combustion of the insulating material to enable the recovery of the metal conductor within the wire or cable. This method has serious practical limitations. In the first place, the metal recovered is charred, i.e., oxidized due to the high temperature required to burn off the insulating material. In the case of copper conductors, combustion results in the loss of approximately 6 percent by weight of the copper which was potentially recoverable. Secondly, the oxidized metal is of a lower grade than unoxidized metal and therefore yields less on the market. Thirdly, the charred insulation, or ash, must be knocked off the inner conductor before the metal is acceptable for smeltering, i.e., marketable. The additional step of knocking off the ash necessarily increases the cost of the method and thereby decreases its commercial value. An additional and very substantial shortcoming of the combustion method is that, without special purpose air pollution abatement equipment, it results in the emission of air pollutants into the air. Many States and other governmental agencies prohibit such emissions. As a result, the reclaimant is required either (i) to transport the scrap to a place where burning is not prohibited or (ii) to install the necessary abatement equipment. In either case, the cost of practicing the method is increased significantly. Lastly, the burning method destroys the insulation and therefore whatever value the insulating material might have is lost.
Another method known in the prior art is to dissolve chemically the insulating material. This method has proved to be relatively uneconomical due to the typically high solids ratio of insulation to inner conductor by weight. For example, the insulation covering a copper inner conductor is typically 28 - 30 percent by weight of the wire. Because of the relatively high solids ratio, the cost of the chemical composition required to dissolve sufficient insulation to yield a pound of metal is too high with reference to the market value of the pound of metal yielded. An additional shortcoming of this method results from the fact that many different insulating materials are used in wires and cables. This fact requires the reclaimant to have various chemical compositions available, each one particularly suited to dissolving a particular type of insulating material.
Still another method of the prior art for the reclamation of insulated wire and cable is disclosed by Wanzenberg in his U.S. Pat. No. 3,342,638, granted on Sept. 19, 1967, involving a special purpose apparatus for heating a mass of insulated wire without burning the insulation, and extruding the insulation while compressing the metal into a solid compact. This method has the disadvantage of requiring the special purpose and relatively complex apparatus disclosed in the aforesaid patent. In addition, this method requires the strands of wire and cable to be assembled in a feed container in substantially parallel linear alignment, a laborous step when the wire to be processed is in the form of a tangled coil or bale.
The present invention accomplishes the objective of reclaiming the metallic inner conductor and the insulating material of scrap wire and cable without the shortcomings and limitations of the prior art. In addition, the metal reclaimed is in its purest form; i.e., it is not degraded by the process of reclamation taught by this invention. Most importantly, however, the present invention enables the recovery of metal at a cost significantly less than has heretofore been possible by the methods known and practiced in the trade.
BRIEF SUMMARY OF THE INVENTION
The present invention is a method for physically separating and reclaiming conducting and insulating materials from structural combinations of the same, such as are found in insulated wire and cable. The invented method is based upon, and is one means for exploiting, the discovery that certain chloronated hydrocarbon solutions cause most of the insulating materials commonly used in wire and cable manufacture to swell and soften. When in a swollen and softened state (as caused by a chlorinated hydrocarbon solution), the insulating materials typically lose their strength and will readily break away from the inner conductor if subjected to a random and cascading motion. A preferred chlorinated hydrocarbon solution is methylene chloride because during the time typically required to remove insulation, it has substantially no effect chemically on copper, the most commonly used metal for the inner conductor of wire and cable. In addition, methylene chloride has only a relatively slight chemical effect on most of the insulating materials used in wire and cable manufacture. Therefore, the use of methylene chloride as a stripping agent also enables the reclamation of the insulating materials, many of which have commercial value such as neoprene and various rubbers. In addition to its low order of reactivity on insulated wire and cable, methylene chloride is also a preferred stripping agent because (i) it can be recovered and recycled inexpensively, thereby adding substantially to the cost-effectiveness of the invented method; (ii) it is readily available throughout the world at a low price; (iii) it has a relatively low toxicity as compared to other chlorinated hydrocarbons; and (iv) it has no flash or fire points.
The present invention, therefore, comprises the process steps of (i) soaking a mass of wire or cable in a bath of a chlorinated hydrocarbon solution, (ii) subjecting the mass to a random tumbling or cascading motion until the insulating material and conducting metal separate; (iii) reclaiming the metal; (iv) recovering and recycling the chlorinated hydrocarbon solution; and (v) reclaiming the insulating material. The reclaimed conducting metal is typically free of residue or contaminants. After recovery, the chlorinated hydrocarbon quickly evaporates. The metal requires no rinsing or other special handling (such as the removal of ash as required by the prior art method of burning off the insulation). The metal is typically of the highest grade and therefore commands a top price on the metals ' salvage market (prior to smelting).
Thus, it is a principal object of the present invention to enable the economical recovery of valuable metals and insulating materials from scrap wire and cable.
It is another principal object of this invention to provide a method for reclaiming insulated wire and cable which does not degrade the quality or reduce the quantity of materials recovered.
It is another object of this invention to provide a method for reclaiming insulated wire and cable which does not require elaborate and expensive special purpose equipment.
It is still another object of this invention to provide a reclamation method which does not rely upon burning, thereby eliminating air pollution constraints on a reclaimant's operation.
A still further object of the present invention is to enable the processing of scrap wire and cable in the form in which it is typically found, i.e., tangled coils or bales, without laborous untangling or other process steps.
Other objects, novel features and advantages of the present invention will become apparent upon making reference to the following detailed description. The description will also further disclose the characteristics of this invention. Although the invention will be described hereinbelow in terms of a particular example, it should be expressly understood that the description thereof is for the purpose of illustration only and does not limit the scope of this invention.
DETAILED DESCRIPTION OF THE INVENTION
For the purpose of greater clarity and understanding, the detail description of the present invention will be made with reference to a particular example, namely the reclamation of copper from scrap wire and cable utilizing as a stripping agent, a nearly 100 percent solution of methylene chloride, the preferred chlorinated hydrocarbon. The methylene chloride solution is not 100 percent because of the addition of a small amount of neutralizer as described more fully hereinbelow.
A bale of scrap insulated wire and cable is first immersed in a bath of methylene chloride solution. Prior to immersion in the bath, the bale of wire and cable requires no processing. However, in order to ensure the recovery of the highest purity of copper, it is preferable to inspect the bale and to eliminate strands of wire or cable which an inspector can readily determine are types which either (i) contain other metal in addition to or instead of copper and/or (ii) utilize insulating materials on which methylene chloride is not effective as a stripping agent such as, for example, teflon.
The tank in which the bath of methylene chloride is contained should be large enough to accommodate the volume of the typical bales of scrap wire and cable which are to be processed. In addition, the tank must be adapted to being (i) mechanically coupled to a source of power and (ii) set into a particular motion by that source of power. A preferred motion is rotation at a rate in the range from 6 to 72 rpm, because such rotation subjects the bale of wire to a random tumbling or cascading motion which is particularly suited to breaking the insulating material away from the copper conductor after the former has been swollen and softened by the stripping agent. The inclusion of internal vanes within the rotatable tank substantially enhances the process of separation because of the impact of the insulated wire against the vanes during rotation. Of course, the tank containing the bath solution and scrap wire must be capable of being sealed so as to avoid any loss of the solution during the rotation or other motion of the tank.
In the first of two alternative procedures, a bale of scrap wire is immersed in the tank containing the bath of methylene chloride at ambient room temperature. The tank is then sealed, the power source to which the tank is coupled is activated, and the solution heated to a temperature of 104° F, its boiling point, by external conventional heating means. At a temperature of 104° F the solution of methylene chloride causes the insulating material on the strands of wire and cable to become swollen and soft. The motion of the tank, preferably rotation, causes the bale of scrap wire to break apart, thereby facilitating the penetration of the solution into the insulation and speeding up the process of stripping by quickening the heat transfer required. For this reason it is preferred that the rotation of the tank start immediately after the tank is sealed. In addition, as indicated earlier, the motion of the tank contributes to the process of breaking the insulating material away from the copper conductor after the insulation has become swollen and softened. Approximately 65 minutes after the start of the procedure described, the separation of insulating materials from copper is usually complete and the copper may be removed from the tank. No rinsing or other processing is required with respect to the copper recovered. The methylene chloride solution on the metal rapidly evaporates.
In an alternate procedure, a bale of scrap wire is placed in an empty tank. The tank is then sealed and immediately activated, preferably rotated, while methylene chloride, preheated to 104° F, is pumped or otherwise injected into the tank. As in the first procedure, it is preferable to activate the tank immediately after it is sealed, for the same reasons. By this procedure approximately 35 minutes is required to separate the insulating material from the copper conductors. Again no rinsing of the copper is required after its removal from the tank.
At this point in the reclamation process, the tank contains the methylene chloride solution and the residue of swollen insulating material. Recovery of the methylene chloride for reuse is a substantial factor in making the invented method more economical than has heretofore been possible. In addition, as indicated earlier, reclaiming the insulating material for subsequent sale further enhances the commercial value of this method. Recovery of the methylene chloride is by distillation; i.e., evaporation out of the tank and condensation in a separate recovery tank. The techniques and apparatus for distillation are well-known in the trade. Typically, about 95% of the original amount of methylene chloride by volume is recovered by distillation. It is of reusable quality and may be recycled indefinitely. After the recovery of the methylene chloride solution, a mass of insulating material remains in the tank. It can be easily removed for further processing or sale.
It has been observed that the methylene chloride solution recovered by distillation is more acidic than pure methylene chloride solution. This is due to the influence of heat, acidic lubricants and soils typically found on the wire. In addition, certain volatile contaminants, produced during the soaking period, are probably not all separated from the methylene chloride during the distillation step. In order to neutralize the increased acidity of the solution, a suitable neutralizing agent is typically added to the solution prior to distillation and when charging the tank in connection with either of the alternative procedures described hereinabove. Suitable neutralizing agents are sodium hydroxide (caustic soda), lithium hydroxide and potassium hydroxide. Caustic soda is a preferred neutralizer because of its general availability and relatively low price. Caustic soda, each time it is added, is typically added at the rate of 0.4 to 3.0 percent by weight based on the weight of methylene chloride; i.e., 0.4 - 3.0 pounds of caustic soda for each 100 pounds of methylene chloride.
This invention also contemplates the addition of an improved neutralizer or "stabilizer," many of which are known in the industry and generally referred to as "antioxidant inhibitors," "neutral acid acceptors" or "acceptors." Such compounds are typically used to prevent hydrolytic, thermal, oxidative and catalytic degradation.
As indicated earlier methylene chloride is a preferred stripping agent. Other chlorinated hydrocarbons suitable for use as the stripping agent in the invented method include carbon tetrachloride, ethylene dichloride, monochlorobenzene, ortho-dichlorobenzene, trichlorobenzene, chlorobenzene, propylene dichloride, I, I, I-Trichlorethane, perchlorethylene, trichlorethylene, and chloroform.
Although this invention has been disclosed and described with reference to a particular example, the principles involved are susceptible of other applications which will be apparent to persons skilled in the art. It will be understood by those skilled in the art that various changes in detail and application of the invented method may be made therein without departing from the spirit and scope of the invention.